Blank holder and die cushion cylinder having separate adjustable pressures



Sept. 1, 1942 W. ERNST SEPARATE ADJUSTABLE PRESSURES Filed March 29,1940 5 Shets-Sheet 1 m 4 4K I I I F-i l P 2? I I I2 0 L...

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BLANKHOLDER AND DIE CUSHION CYLINDERS HAVING SEPARATE ADJUSTABLEPRESSURES Filed March 29, 1940' 5 Sheets-Sheet 2 FIE'nE Sept. 1, 1942.ERNST W. BLANKHOLDER AND DIE CUSHION CYLINDERS HAVING SEPARATEADJUSTABLE PRESSURES Filed March 29, 1940 FIB-.3

5 Sheets-Sheet 3 v Sept. 1, 1942. w. ERNST 2,294,451

BLANKHOLDER AND DIE CUSHION CYLINDERS HAVING SEPARATE ADJUSTABLEPRESSURES Filed March 29, 1940 5 Sheets-Sheet 4 L 0 N a a Q 7 0 Q I Q Qs; I 1

m 2 r Y l l s i N Q U] r V x r Sept. 1, 1942. w. ERNST 2,294,451

v BLANKHOLDER AND DIE CUSHION CYLINDERS HAVING SEPARATE ADJUSTABLEPRESSURES Filed March 29, 1940 5 Sheets-Sheet 5 Q I Q Q N lA/VE/VTOPMATE/P EPA/67 5 we ATTOF/VEYF Patented Sept. 1, 1942 mm: nouma AND macusmoN cynnmsn mvmc SEPARATE anms'raam PBESSURES Walter Ernst, MountGilead, Ohio, assignor to The Hydraulic Development Corporation, 1110.,Mount Gilead, Ohio, a corporation of Delaware Application March 29,194', Serial N0. 326,709

7 Claims. (Cl. 113-45) This invention relates to presses, and inparticular in hydraulic presses having blank holding arrangements inassociation with drawing de- .vices.

One object or this invention is to provide a hydraulic press having adrawing plunger and a plurality of clamping cylinders which will make itpossible to exert and maintain different pressures in the clampingcylinders, and to vary the pressure in the individual clamping cylindersindependently of each other.

It is another object or this invention to provide a hydraulic presshaving-a drawing plunger and a plurality of clamping cylinders, in whichthe pressure in each clamping cylinder is individually controllable andautomatically maintained .by means associated with said clampingcylinders.

A further object orl the invention consists in providing a hydraulicpress ofthe character' referred to in the preceding paragraph in whicheach clamping cylinder is associated with a variable delivery pump whichautomatically .varies its flow of fluid so as to maintain the desiredpressure in the clamping cylinder pertaining thereto.

It is a still further object oi the invention to provide a hydraulicpress having a drawing plunger, a plurality of clamping cylinders, andcushioning cylinders which will make it possible individually to .varyand maintain the pressure in each clamping and cushioning cylinder.

These and other objects and advantages will appear more clear from thefollowing specification in connection with the accompanying drawings inwhich:

' Figure 1 diagrammatically illustrates a press according to the presentinvention at the beginnin'g of the downward stroke of the clampingplungers;

Figure 2 is a view similar to Figure 1, but showing the press at the endof the clamping stroke;

Figure 3 is a section along the line 3-3 of Figure 1;

Figure 4 is a section similar to Figure 3 with the exception that thepumps associated with the clamping cylinders are replaced by pressurereducing valves;

used in connection with the hydraulic circuit of Figure 'I. a

The press as illustrated in the drawings comprises a bed I and a head 2spaced from and connected with each other by strain rods 3 and nuts 4.The head 2 carries a main cylinder 5 and clamping cylinders 6. The maincylin'der 5 has reciprocably mounted therein a plunger 1] carrying apress platen 3 which, in its turn, supports an upper die 8. The lowerend of the main cylinder 5 is provided with packing material IIcompressed by a gland H for preventing leakage from the main cylinder.Similarly, each of the clamping cylinders i is provided with packingmaterial I2 compressed by a gland 13 for preventing leakage from therespective clamping cylinder.

Through each gland I3 and packing material I2 of the clamping cylindersis passed a clamp ing rplunger l4 carrying a blank holder IS. The pressplaten 3 and blank holder 1 5 have lugs" and I1 respectively throughwhich a rod l3 with nuts I! and 20 is passed so that the blank holder I!is lifted by the press platen when the latter has moved a predetermineddistance away from the blank holder. The main cylinder 5 is connected atits upp'r end with a conduit 2| leading to one port 22 of a variabledelivery pump 23, while the other port 24 or the pump 23 is connectedwith a conduit 25 leading to the lower end or the cylinder 5.

Each of theclamping cylinders 3 is connected by means of a conduit 26with a conduit 21 leading to a two-way valve 23 and having mountedtherein a check valve 23 which opens in the direction of the arrow Aonly. The two-way valve 23 comprises a cylinder 33 closed at its ends bypacking material 3| and 32 and heads 33 and 34. The cylinder 33 hasthree aligned bores 35, 33 and 31 of a diameter corresponding to thediameter of pistons 33 and 33 connected'with a push rod 40. The bores 35and 36 are separated from each other by a chamber 4! having a diametergreater than those 01' the pistons 33 and 33. Similarly the bores 36 and31 are separated by a chamber 42 which has a diameter likewise greaterthan those of the pistons 33 and 33.

A conduit 43 leads from the chamber 42 to a fluid tank 44, while theconduit 21 leads into the chamber 4|. The fluid tank 44 has mountedtherein a valve 45 for releasing the pressure in I the upper portion ofthe main cylinder 5 at th' beginning of the return stroke of theplunger 1. This valve 45 comprisesa casing 46 having two be springchamber 41 and 43 and two cylinder bores 49 and 56. The cylinder bore 46is adapted to communicate through an aperture with the fluid tank 44,and similarly an aperture 52 is provided for effecting communicationbetween the cylinder bore 56 and the fluid tank 44. Furthermore, achannel 56 is provided for effecting a communication between the twobores 49 and 56. A conduit 54'leads from the bore 56 to the conduit 2|,while a conduit 55 leads from the cylinderbore 49 to the conduit 25. Aconduit 56 branches off from the conduit 54 and leads to the cylinderbore 49. Reciprocably mounted in the cylinder bore 49 is a valve member51 with two pistons 56 and 59 which, in the position shown in Figure 1,close oi! the channel 53 and the aperture 5I.

Connected with the piston 59 is an abutment 66 which is engaged by aspring 6i provided in the spring chamber 41 and urging the valve member51 toward the right. Similarly, a spring 62 in the spring chamber 46engages an abut-' ment 63 connected with a piston 64 reciprocable in thecylinder bore 56. The piston 64 forms a part of the valve member 65which carries a second piston 66. In the position shown in Figure 1, thepiston 64 closes the aperture 52, while the piston 66 preventscommunication between the conduit 54 and the channel 53. A conduit 61leads from the fluid tank 44 to the port 24 of the pump 29 and hasmounted therein a check valve 66 which opens only in the direction ofthe arrow B.

A further conduit '69 leads from the fluid tank 44 to a chamber 16 of asurge valve generally partition 19 is provided with a bore through whichis passed a piston rod 16 carrying a piston 11. A spring 16 is mountedbetween the parti-' tion 13 and the piston 11 urging the piston 11upward. The partition 15 is likewise provided with a bore 19 which has adiameter greater than the diameter of the piston rod 16. The cylinderbore 14 has also reciprocably mounted therein a piston 66 urged by aspring 6| to its uppermost position. In this uppermost position thepiston 66 closes ofl a port 62 connected with the conduit 2| by aconduit 63. A conduit 64 leads from the lower part of the cylinder bore14 to the conduit 54,-while a conduit 65 leads from the upper portion ofthe cylinder bore 12 to the conduit 55.

The push rod 46 passing through the two-way valve 26 has adjustablymounted thereon two cams 66 and 61 having grooves 66 and 69respectively. The cams 66 and 61 cooperate with pins 96 and 9| carriedby an arm 92 connected with the press platen 6. The arm 92 has a bore 93through which the cams 66 and 69 may pass. The pins 96 and 9| are urgedtoward the bore 99 by springs 94 and 95 provided in arm 92 so that thepins may engage the groove 66 or 69 as the case may be. The lower end ofthe push rod 46 is passed through a lug 96 connected with the bed I. Thebed I carries cushioning cylinders 91 having reciprocably mountedtherein cushioning plungers 96 passing through packing material 99compressed by a gland I66 and carrying the lower die I6I.

According to the embodiment of Fig. 3, each of the clamping cylinders 6is connected with the pressure side of a variable delivery pump I62 bymeans of the conduit 26. The suction side of each delivery pump I62 isconnected by means of a conduit I66 with a fluid tank I64 which, ifdesired, may be connected with or form a part of the fluid tank 44.Branching oi! from the conduit 26 is the conduit 21 leading to a channelI66 of the check valve 29 (see also Fig. 1). The channel I66 is normallyclosed by a ball I66 arranged in a chamber I69 of the check valve 29.The chamber I69 communicates through a channel II6 with the chamber H ofthe two-way valve 26. As will be clear from the foregoing, the fourcheck valves 29 prevent the pressure from equalizing in the fourclamping cylinders 6, whereas the two-way valve 26 is adapted to openthe clamping cylinders to exhaust.

The variable delivery pump I62, shown in detail in Figure 5, comprises apump casing III having connected to one side thereof, for instance bymeans of screws 2, a hollow arm H3. Telescoped in the hollow arm H9 is aspring casing II4 engaged by one end of the spring II5. The other end ofthe spring II5 abuts the wall-H6 of the hollow arm II6. Reciprocablymounted within the pump casing III is a flow-control member I I1 adaptedto vary the flow of the variable delivery pump by moving a secondaryrotor relatively to a primary rotor. Moreover, a pluralit of radialpistons and cylinders (not shown) are operatively connected with saidrotors. The arrangement of these rotors and the interior of the pump iswell-known to those skilled in the art and for more detailed descriptionthereof, reference may be had to U. S. Patents Nos. 1,964,244 and2,041,172.

Threaded into or otherwise connected with the flow-control member H1 isan adjusting rod 6 which passes through the pump casing III and the wallII6 of the hollow arm H3 and is provided with a threaded portion I I9passing through the spring casing H4. The threaded portion H9 is engagedby a nut I26 provided with a handwheel I2I so that by rotation of thehandwheel I 2| in one direction; the spring casing |l4,may be moved intothe hollow arm II3 thereby increasing the thrust of the spring, whereasthe rotation of the handwheel I2I in the opposite direction allows thespring II5 to expand. Screwed to or otherwise connected with theopposite'side of the'pump casing is a cylinder I22 having a cylinderbore I26, closed at its outer end by a gasket I24 and a cylinder headI25. Reciprocably mounted in the cylinder bore I26 is a piston I26connected with a push rod I21 threaded into the flow-control member 1.Adjacent the cylinder bore I23 and adapted to communicate therewith is abore I26 having a diameter greater than the diameter of the cylinderbore I 23 and communicating through a conduit I 29 with the pressureside of the pump I62. Leakage from the bore I26 toward the interior ofthe pump casing III is prevented by packing material I66 providedbetween the pump casing III and the cylinder I 22 and surrounding thepush rod I21.

As will be clear from the foregoing, the spring II5 tends to hold theflow-control member in a position determined by the setting of thespring, thereby maintaining a predetermined flow of fluid of the pumpI62. However, if the fluid pressure of the pump exceeds a predeterminedvalue, this pressure will be conveyed from the pressure side of the pumpthrough the conduit I29 into the bore I26 where it acts upon the pistonI 26 and moves the latter somewhat toward the right until equilibrium isestablished between the pressure acting upon the piston I26 and thevalves I3I I thrust of the spring acting in the opposite direction. Themovement of the piston I26 toward the right causes theflow-control'member to restrict the flow of fluid of the pump I02. Inthis way, the pump I02 automatically maintains the desired fluidpressure.

According to the embodiment of Figure 4, the pumps I02 are replaced bypressure reducing which are supplied with fluid from a common variabledelivery pump I42. Since this pump as shown in the drawing lacks theservomotor conduit I29 of the pump I02, provision is made for preventingexcessive pressure in the conduits between the pump I42 and the pressurereducing valves I3I. To this end aconduit I43a comprising a relief valveI42a connects the pump I42 with the tank I44. The relief valve 2:; is soset that its opens towards the tank I44 at a pressure slightly higherthan the denied pressure in the clamping cylinders. Aside from the abovementioned features the arrangement shown in- Figure 4 corresponds tothat of Figure 3 and the corresponding parts are designated with thesame reference numerals, however with the additional letter a.

The pressure reducing valve I3I comprises a body member I 32 (see Figure6) having reciprocably mounted therein a plunger-I33 guided by a guidering ably of U-shaped leather mounted between rings I36 and I31. Ashoulder I38 on the body forms a seat for the ring I36, and a screw plugI39 threaded into the body I32 presses the ring I31 against the packingI35.

The body I32 of each of the four pressure reducing valves shown in Fig.4 is provided with an inlet I40 connected with a conduit I03a leading toa manifold I4I which is connected with the pressure side of the variabledelivery pump H2. The suction side of the variable delivery pump I42communicates through a conduit I43 with a fluid tank I44 which may beconnected with or fonn a part of the fluid tank 44. The inlet I40 (seeFig. 6) communicates openings I46 in the ring I31 with a central chamberI41 in theend of the plunger I33. A plu- I34 and by a packing I35preferthe sleeve I55 connected with the casing I54. The upper end of thespring I50 rests against the v nut I59 while the lower end of the springabuts the washer I49. The stem I58 is provided with a handwheel I62 bywhich it may be rotated, and since the nut I59 cannot rotate with thestem I51 due to the engagement of its pins I6I with the slot I56, therotation of the handwheel will cause the nut I59 to move longitudinallyof the casing so as to vary the thrust of the spring I50.

A. passage I63 affords communication between the chamber I5I and theinterior of the casing I54 when the plunger I33 is moved inwardlysufliciently to lift the washer I49 off its seat onthe body'and thusopen the communication, it being understood that the interior ofthecasing I54 is always under more or less' pressureby reason of thefluid entering between the washer I49 and the sleeve I55 and around theplunger I33.

The valve opens in thefollowing manner: The hydraulic pressure enteringthrough the inlet I 40 and the passage I45 is supplied to the plungerI33 within the chamber I41 and also at the end of the plunger I33. Thispressure being greater than that of the spring I50 moves the plungerinward. As soon as the ports I48 pass beyond the packing I35 and opencommunication with the chamber I5I, .thefluid will pass therethrough andthrough the passage I63 into the spring chamber, thus affording a backpressure upon the plunger I33 in addition tothe pressure of the springI50. The pressure on the two sides. of the plunger I33 will thereforetend to arrive at a balance, and it is evident that the pressure at thelow pressure outlet I52 will be r equal to the high pressure minus thepressure 'acting from the interior of the shell I55 upon by an inclinedpassage I and rality of small ports I40 radiate from the chamber I41 andpass through the plunger. The inner end of the plunger I33 is providedwith a shoulder which rests against a washer I49 which is forcedoutwardly by a spring I50 and therefore tends to resist the inwardmovement of the plunger. A chamber I5I within the body I32 communicatesby means of an outlet I 52 with a conduit 26a leading to the respectiveclamping cylinder 6a and the check valve 29a. Since the clampingcylinder 6a and check valves 29a fully correspond to the clampingcylinders 6 and check valves 29 respectively, no further explanation isnecessary. The ports I48 are adapted to communicate with the chamber I5Iwhen the plunger is forcedinwardly by a predetermined amount.

Screw threaded into the body I is a casing I54 which is welded orotherwise fastened to a sleeve I55 which is preferably of non-corrosivemetal.

' plunger their ends projecting into.the slots I56 and thereby preventrelative rotation between the nut and the washer I49. When the pressureat the outlet I52 increases, this .pressurewill be conveyed through thepassage I63 to theinterior of the sleeve I55 and act therefrom upon thewasher I49 so as to move the plunger I33. downwardly,

thereby restricting the flow of fluid through'the ports I48 into thechamber I5I. In this way the desired pressure at the outlet I52 will beautomatically maintained.

Referring now to Figure 7 illustrating the hydraulic circuit for thecushioning cylinders 91, it willbe noted that each cushioning cylindercommunicates through a conduit I64 with a check valve I65. This checkvalve I65 corresponds to the check valve I06 of Figure 3 and comprises achamber I66 communicating through a channel I61 and a conduit I68 withthe conduit I64. A further conduit I69 which may be closed by a ball I10communicates with a conduit I'1I leading into a conduit I12 which, inits turn, is connected with the pressure side of a variable deliverypump I13. The suction side of the variable delivery pump I13 isconnected with a fluid tank not shown in Figure 7. The conduit I64 isalso connected with a relief valve I14 shown indetail in Figure 8.

The relief valve I14 consists of a casing H5 having a bore I16 whereinreciprocates a valve I11. Arranged between the valve plunger I11 and thebore I16 is a tubular member I18 having a longitudinal bore I19 andcross bore I80, the cross bore I communicating'with an annular chamberopening into a transverse bore I8I in the casing I15. The endiconnection I82 of the conduit I64 is held in communication with thebore I16 by means of a collar I83 engaging the threaded portion I84 ofthe casing I15, whereas a pipe connection I85 similar. to the pipecontransverse bore III by means of the threaded" ,collar I88 engagingthe threaded portion I81 of the casing I15.

Mounted on the upper portion of. the casing I15 is a tubular cap I 88secured thereto by screws I89. Within the cap I88 is a coiled springI90, one end of which engages an enlargement I9I upon the upper end orthe valve plunger I11, whereas the opposite end engages a button I92 incontact with an adjusting screw I93 threaded through a bore I94 in theupper end of the cap I88. Surrounding and covering the adjusting screwI98 is a hollow nut I95 which serves to protect the adjusting screw I93and also to lock it in its adjusted position.

As will be clear from the foregoing description, the spring I90 willnormally hold the plunger I11 in such a position that the latterprevents communication between the bore I19 and the transverse bore I8I.However, whenthe pressure inthe bore I19 exceeds a predetermined valuedetermined by the setting of the spring I90, the plunger I11 will belifted to such an extent that pressure fluid from the respectivecushioning cylinder 91 may pass through the conduit I04 and the bore I19into the transverse bore I8| and from there to the fluid tank. The fluidexpelled from the respective cylinder 91 cannot escape to the conduit 1|since the communication between the conduit I58 and the conduit I" isclosed bythe ball I10.

The operation of the device is as follows:

If a drawing operation is to be effected, the

workpiece I 96 is placed on the bed I and the hydraulic pump 23 isstarted and its control set so that fluid pressure passes through theconduit 2|. The plunger 1 first moves downwardly by gravity and thespace above the plunger is filled by fluid from the pump 23 and from thetank 44 through the conduit 69 the surge valve 1| and the conduits 82and 2|. It will be understood that the suction eifect in the conduit 2|and the conduits 54 and 84 causes the piston 80 of the surge valve tomove downwardly so as to eflect communication between the surge'valvechamber 14 and the conduit 82 connected therewith. At the same time theclamping plungers I4 move downwardly by gravity and fluid from thevariaable delivery pumps I02 (Figure 3) or the variable delivery pumpI42 (Figure 4) flows through the into the clamping cylinders. Thecushioning cylinders 91 are assumed to have been filled with fluidduring the previous retraction stroke, so

. 1 the liquid in the lower portion of the main cylinder 5 escapesthrough the conduit 25 to the 09. Just before the upper die 9 contactsthe workpiece I98, the pins 90, 9| of the arm 92 engage the groove 88 ofthe cam 86 and move the rod downwardly so as to shift the pistons 38 and39 of the two-way valve 28 for interrupting the communication betweenthe conduits 21 and 43. It will be understood that the rod 40 waspreviously held in its upper position by friction between the rod 40 andthe packing material 3|, 32 surrounding the same. When the pistons 88and 39 have reached their lower-most position while the downwardmovement of the die 9 still continues, the pins 90 and 9| click out ofthe groove 83, slideover cam 81 and at the end of the pressing ordrawing operation are below the cam 81. When the drawing operationproper starts, the die 9 presses the workpiece I96 into the lower dieagainst the resistance of the liquid in the cushioning cylinders 91.Fluid from the cushioning cylinders 91 can escape only through therelief valves I14 and the pressure in each cylinder 91 can be controlledby the adjustment of its respective relief valve, 1. e. by setting thescrew I93 of the valve I14.

After the upper die 9 has moved the desired distance and completed itsdrawing operation the flow through the pump 23 is reversed by anydesired means so as to initiate the retraction stroke of the plungerpl,When the pins 90, 9| during this retraction stroke engage the groove 89of the cam 81, they move the control rod 40 and the pistons 38, 39 inthe two-way valve 28 to their uppermost position indicated in Figure 1,thereby establishing communication between the conduits 21 and 43 sothat liquid from the clamping cylinder G -may escape through theconduits .21, the check valves 29. the two-way valve 28, and the conduit43 into the fluid tank 44. When the retraction stroke oi! the plunger 1is about to be conduit 25 or conduits H311 and 260 respectively suctionside 24 of the pump 23. As soon as the upper die 9 contacts theworkpiece I98, pressure starts to build up in the main cylinder 5 abovethe plunger 1 and acts through the conduits 2| and 54 upon the piston 59of the valve member 85 thereby moving the valve member against thethrust of the spring 52 toward the left so as to eflect communicationbetween the conduit 54 and the channel 53. Furthermore, the pressure inconduct supported by the spring 18 moves the piston 11 upward while thespring 8| of the surge valve 1I' moves the piston 80 engaged therebylikewise upward so as to close commupreviously the piston. 66 wasmovedtoward the left, fluid from the upper portion of the main cylinder5 may now escape through the conduits 2|, 54 and 56 into the cylinderbore 49 from where it flows through the apertures 52 into the tank 44.Furthermore, liquid may escape from the conduits 2|, 54 and 56 into thecylinder bore 49 and from there through the channel 53 and the aperture52 into the tank 44.

The relief of pressure from the upper portion of the main cylinder 5through the valve 45 enables the pressure in the conduit 55- to move thepiston 11 of the surge valve 1| downwardly so as to push the piston 80against the thrust of the spring 8|, thereby efiecting communicationbetween the conduit 2| and the conduit 69 so that the liquid from theupper portion of the main cylinder 5 may now escape through thelast-mentioned conduits into the surge tank. The pressure fluiddelivered by the pump 23 through the conduit 25 into the lower portionof the main cylinder 5 now moves the plunger 1 upwardly. A portion ofthe pressure fluid also flows from the port 24 through the conduit 25ainto the cushioning cylinders 91 so as to flll'the latter and tonication between the conduit 03 and the conduit ra se t e cushioning pers to the po they occupy at the beginning of the drawing operation.

As previously mentioned, when the fluid pres-- sure in the clampingcylinders 6 exceeds a predetermined pressure, the delivery of the pumpI02 is automatically restricted so'that the desired pressure issubstantially maintained. If for some reason during the drawingoperation the pressure in the clamping cylinders should still exceed apredetermined value, the respective check valves 29a come into operationso as to release the pressure until it again reaches the allowablevalue. As will be clear from the foregoing description, each clampingcylinder is individually controlled and may be individually adjustedaccording to the desired pressure in the repsective clamping cylinder. Asimilar automatic control of the clamping cylinders is eifected when thepumps I92 in the circuit of Figure 3 are replaced by the reducing valves|3l shown in Figure 4. In the latter case only one pump, viz. pump I42,

supplies fluid to the clamping cylinders, and the pressure reducingvalves l3| automatically maintain the desired individual pressures inthe clamping cylinders 6a according to the setting of the respectivesprings I50 in the pressure reducing valves I3I, as previouslyexplained. The relief valves I88 associated with the cushioningcylinders prevent undue pressure in the cushioning cylinders, whichpressure may be determined for each cushioning cylinder individually bythe setting of the respective springs I90.

It will be understood that I desire to comprehend within my inventionsuch modifications as come within the scope of the claims and theinvention. For instance, it desired, the check valves 29 and 29a may bereplaced by check valves in which the closure member is normally held inclosed position by a spring. Also a constant delivery pump may besubstituted for the variable delivery pump I42 or, preferably, the pump2 with the conduit 3a and check valve 211 may be replaced by the selfcontrolling variable de livery pump 12.

Having thus fully described my invention what I claim as new and desireto secure by Letters Patent is:

1. A hydraulic press comprising in combination a drawing plunger, aplurality of fluid operable clamping pistons reciprocable in clampingcylinders, a plurality of variable delivery pumps respectivelyassociated with said clamping cylinders for supplying fluid thereto,said pumps being adapted automatically to vary the supply of fluid tosaid cylinders in response to the pressure prevailing in said cylinders,means adapted to prevent equalization of the pressure in said clampingcylinders, and valve means adapted to allow escape of fluid from saidclampin cylinders during the retraction stroke of the drawing plunger,and means extending from said drawing plunger,

said extending means being located out of conand adapted automaticallyto vary the flow of fluid to said cylinder-piston-assemblies formaintaining' a predetermined pressure therein, the

pressure of each clamping cylinder-piston-assembly being variableindependently of one-another, a plurality of cushioning cylinders withcushioning plungersreciprocable therein, a plurality of individuallycontrollable pumps for supplying fluid to said cushioning cylinders andmeans associated with said pumps and adapted individually to vary andmaintain the fluid pressure in said cushioning cylinders. I

3. A hydraulib press comprising in combination a drawing plunger, aplurality of fluid operable clamping members for holding a workpieceduring the drawing operation of said drawing plunger, a plurality ofpumping means operable independently of each other individuallysupplying pressure fluid to said clamping members, means associated withsaid clamping members and adapted automatically to vary the supply offluid to the respective clamping member and to maintain a predetermineddifferent pressure thereon, a pinrality of cushioning memberscooperating with said drawing plunger during the drawing operation,further pumping means for supplying fluid to said cushioning members,and a plurality of relief valves associated with said cushioning membersoperable at the attainment of a predetermined pressure on said clampingmembers.

4. A hydraulic press comprising in combination a main cylinder, adrawing plunger reciprocable in said main cylinder and supporting anactuating member, a plurality of fluid operable clamping plungersreciprocable in clamping cylinders and adapted to hold a workpieceduring rality of independently operable fluid supply means respectivelyassociated with said clamping cylinders, means operatively connectedwith said fluid supply means and adapted automatically to control thesupply of pressure fluid from said fluid supply means to saidclampingcylinders to create and maintain different predetermined pressures indifferent clamping cylinders, and valve means comprising a reciprocablevalve and actuating means therefor located adjacent to said actuatingmember, said actuating means operable by said actuating member torelease all fluid pressure in said clamping cylinders -in response to apredetermined point of travel of said drawing plunger during theretraction stroke thereof.

5. A hydraulic press comprising in combination a drawing plunger, aplurality of fluid operable clamping pistons reciprocable in clampingcylinders, a plurality of variable delivery pumps respectivelyassociated with said clamping cylinders for supplying fluid thereto,said pumps being adapted automatically to vary the supply of fluid tosaid cylinders in response to the pressure prevailing in said cylinders,adjusting means associated with said pump for maintaining diflferentpredetermined pressures in different clamping cylinders, a plurality ofcushioning members cowith said cushioning members and having meansadapted to maintain different pressures on difierent cushioning members,and means adapted to release the pressure in said clamping cylinders inresponse to a predetermined point of travel of I said drawing plungerduring the retraction stroke pendent pumps connected into saidclosed'hyl5 draulic system eachsupplying fluid to each 01' theblankholder rams.

whereby they are hydraulically actuated in one direction onl a commonvalve controlling mechanism therefor actuated by the movement of aplatenattached to the main ram, means interconnecting said main ram andblankholder rams whereby said main ram moves said blankholder rams inthe opposite direction, and a plurality of independent pumps connectedinto said closed hydraulic system each supplying fluid to each of theblankholder rams, and means of adjusting the fluid pressure from each ofsaid blankholder ram pumps.

WALTER ERNST.

